Filter apparatus

ABSTRACT

Disclosed is a filter apparatus comprising a filter housing having a filter head ( 3 ) and a filter bowl ( 7 ), which housing accommodates a filter element that separates a non-filtrate side ( 15 ) from a filtrate side ( 17 ), and comprising a differential pressure measurement device ( 59 ), which indicates at least a blockage of the filter element during filtration operation and which has a measurement piston ( 91 ) that is guided in a measurement housing ( 88 ) in a longitudinally displaceable manner, an end face ( 90 ) of which piston being subjected to the instantaneous pressure of the non-filtrate side ( 15 ), and the opposite end face of the piston being subjected to the instantaneous pressure of the filtrate side ( 17 ), each instantaneous pressure passing into the measurement housing ( 88 ) via at least one conduit ( 57, 61, 65, 89 ). The invention is characterised in that at least a section ( 57, 61 ) of the conduit is arranged in an element cap ( 43 ) of the filter element.

The invention relates to a filter device, comprising a filter housing having a filter head and a filter bowl, which housing accommodates a filter element that separates a non-filtrate side from a filtrate side, and comprising a differential pressure measurement device, which indicates at least a blockage of the filter element during the filtering operation and which has a measurement piston that is guided in a measurement housing in a longitudinally displaceable manner, with the instantaneous pressure of the non-filtrate side being applied to an end face of said piston and the instantaneous pressure of the filtrate side being applied to the opposite end face of said piston, each instantaneous pressure arriving in the measurement housing via at least one channel run.

Filter devices of this kind having a variety of different designs and with exchangeable filter elements which conform to various specifications, are prior art. The filter elements are used in such filter devices for maintenance of fluids, in particular in oil-hydraulic systems. In order to guarantee the operational reliability of such units, which is largely dependent on the faultless performance of the filter devices, such filter elements are commonly monitored with respect to their dirt retention capability by means of differential pressure measurement (DE 10 2005 043 752 B3) so as to avoid the risk of breakdowns or even damage occurring due to overloading, which can result in significant economic losses in the case of expensive systems.

In view of these problems, the problem addressed by the invention is to provide a filter device of the type described above, which is simply constructed and can be produced in a cost-efficient manner.

According to the invention, this problem is solved by means of a filter device which has the features of claim 1 in its entirety.

According to the characterizing portion of claim 1, a significant distinguishing feature of the invention is that at least a part of the channel run, by means of which the instantaneous pressure of the non-filtrate side arrives at the measurement housing of the measurement device, is arranged on the filter element in an element cap thereof. Because the element cap in the filter elements in question can be produced in an economical manner by means of injection molding, in particular from a plastic, with a channel run integrated therein, this allows particularly cost-efficient production of the device as a whole. This element cap with the integrated channel run particularly preferably forms a receiving part forming a casing for an end of the filter material of the filter element. The end of the filter material is particularly preferably accommodated in an adhesive bed of the receiving part. However, it is also possible to provide the end of the filter material with a separate end cap, which is then in turn integrated or accommodated in the receiving part of said element cap with the channel run.

In advantageous exemplary embodiments, the part of the channel run arranged in the element cap ends with its one free end on the non-filtrate side of the filter element and with its other free end in a collection chamber, which protrudes from the external circumference of the element cap and is delimited at opposite end faces in a sealing manner on the one hand by a cover part which is arranged in a detachable manner on the top side of the filter head and on the other hand by parts of the filter head. This means that two opposite boundary walls of the collection chamber are formed by device parts which are already present, namely, the cover part and the filter head, resulting in a corresponding material saving for the element cap itself.

With regards to the formation of the additional parts of the channel run extending up to the measurement device, the arrangement can advantageously be such that the collection chamber as part of the channel run has at the base side a passage formed in the filter head, to which a transverse channel extending in the measurement housing is connected, which leads by means of its other free end to the back end face of the measurement piston.

The measurement piston can be pressurized with an energy store, such as a compression spring, which seeks to displace the measurement piston in the backwards direction, with the front end face of the measurement piston abutting an end piece of the measurement housing, which comprises a passage as an additional part of the channel run, at which the instantaneous pressure on the filtrate side is applied.

As regards the design of the part of the channel run located in the element cap, the arrangement can advantageously be such that the part of the channel run in the element cap of the filter element that opens into the collection chamber overlaps the top end of the filter material and follows the cover part in a parallel manner, with the other part of the channel run, arranged perpendicular thereto, being accommodated by a receiving support extending in the radial direction and being guided, with a projection, on the inner side of the filter element which forms the non-filtrate side.

In particularly advantageous exemplary embodiments, the collection chamber is a component of an annular sealing system, which is arranged at the external circumference on a receiving crown, which is held by means of a ring of radially arranged supports, which are connected to an end-face receiving part for the top end of the filter material, with a conical guide body which extends axially from the internal circumference of the receiving part into the inner side of the filter element being connected to the receiving part, the supports continuing on the inner side of said guide body, one of which supports forms the receiving support for the part of the channel run extending to the non-filtrate side. In this design, the receiving crown, the supports, the receiving part and the guide part, integrally connected to each other, form the element cap.

The arrangement can also advantageously be such that the sealing system has a molded seal at the external circumference, which surrounds a surrounding wall of the receiving crown of the element cap. By means of the thus formed external enclosure of the receiving crown, the sealing system at the same time forms the housing sealing of the entire fluid system relative to the environment.

For the installation of the measurement housing, the filter head can have, at the point of the intervention of the differential pressure measurement device, a projecting connection wall, into which the measurement housing is screwed at the end face.

In particularly advantageous exemplary embodiments, as part of the differential pressure measurement device, projecting further towards the outside, an evaluation unit is connected to the measurement housing which is to this extent formed closed, which evaluation unit indicates to an observer, in particular in an optical manner, whether the filter element in filtering operation is blocked or is still capable of filtering.

In one particularly advantageous formation of the differential pressure measurement device, the measurement piston of the measurement device has a permanent magnet which, in the filtering-capable state of the filter element and acting against the action of an energy store, in particular in the form of a compression spring, holds a permanent magnet of an evaluation piston, which is guided in a housing of the evaluation unit in a longitudinally displaceable manner, in a position which it leaves and moves in the direction of an additional position as soon as the permanent magnet of the measurement piston moves away from the permanent magnet of the evaluation piston due to the constant instantaneous pressure on the back end face and due to the falling instantaneous pressure on the opposite, front end face of the measurement piston brought about by a blockage of the filter element. This provides an indication that clearly signals the transition from the filtering-capable state to the blocked state of the filter element, which indication is also advantageously suitable for an electric signaling, for example by means of a sensor that recognizes the position of the evaluation piston in a contact-free manner.

The invention is explained in detail below with reference to an exemplary embodiment depicted in the drawings, in which:

FIG. 1 shows, in a schematically simplified perspective oblique view and cut open and truncated in the longitudinal direction, an exemplary embodiment of the filter device according to the invention;

FIG. 2 shows, on an enlarged scale compared with FIG. 1, and truncated in the longitudinal direction, a perspective oblique view of the separately depicted filter element of the exemplary embodiment;

FIG. 3 shows a perspective oblique view, depicted further enlarged and cut open and broken off in the longitudinal direction, of only the element cap-comprising top end region of the filter element of the exemplary embodiment and

FIG. 4 shows a depiction, shown on the scale of FIG. 3, cut open and broken off in the longitudinal direction, of only the differential pressure measurement device-comprising top partial region of the exemplary embodiment of the filter device.

With reference to the attached drawings, the invention is explained using the example of a so-called in-tank filter device, in which the filter housing 1 has a filter head 3, on which a fastening flange 5 is situated at the outside. By means of this fastening flange, the filter housing 1 can be mounted on the edge of a top wall opening of a storage container or tank (not depicted) in such a way that a filter bowl 7, which connects to the bottom end of the filter head 3, extends in the vertical direction into the inside of the tank. The length of the filter bowl 7 depicted truncated in FIGS. 1 and 2 is dimensioned such that the bottom end 9 of the filter bowl 7 is situated below the lowest level of fluid, e.g. hydraulic oil, which can be expected during operation. In the design as an in-tank filter device, the filter bowl 7 in the form of a relatively thin-walled circular cylinder is fixed to the filter head 3 by means of a crimping 11. It shall be understood that the invention can be used not only in in-tank filter devices, but also in other types of filter devices, in which a differential pressure measurement device monitoring the operational state of the associated filter element is provided.

For the filtering operation, in which a filter element 13 which can be received in an exchangeable manner in the housing 1 can be flowed through from its inner side 15 which forms the non-filtrate side to its outer side 17 which forms the filtrate side, an inflow housing 19 is located at the bottom end 9 of the filter bowl 7, which inflow housing forms, at its top opening 21 leading to the inner side 15 of the filter element 13, a base 23 which extends radially outwards, the circumferential edge 25 of which surrounds the bottom end 9 of the filter bowl 7. The filter element 13 has an end cap 29 at the bottom end of its hollow cylinder-shaped filter material 27, which end cap engages with its end annular body 31 into the opening 21 of the inflow housing 19. A flap valve 33, which is arranged at the central passage 35 of the end cap 29, opens for the flow of the fluid, which flows from the inlet connection 37 of the inflow housing 19 to the inner side 15 of the filter element 13. In the filtering process, which occurs from the inside outwards through the filter material 27, the filter material 27 is supported against the flow forces by means of an external sheath 39, which has a perforation, which is indicated in FIG. 2 simply by a row of holes 40. In the real embodiment, the perforation extends over the entire surface of the sheath 39 which forms a kind of external support tube. Instead of a sheath with perforations, a grid structure or the like could also be provided. For the purpose of the outlet of the filtrate from the outer side 17 to the tank interior, window openings 41 are formed in the filter bowl 7. In accordance with the prior art which applies to in-tank filters, the window openings 41 are not arranged over the entire length of the filter bowl 7, but instead only in selected surface areas. For example, the window openings 41 can, in accordance with the teaching provided in this respect by EP 2 249 941 B1 and with adaption to the operational fluid level of the tank, be arranged in such a way that any gas bubbles located in the cleaned fluid can be separated and/or can be collected for a discharge.

As is shown more clearly by FIGS. 2 to 4, the filter element 13 has at its top side a specially formed element cap 43, which is injection molded from a plastic material. As the central component, the element cap 43 has a receiving part 45 in the form of a planar annulus, which, as is standard in filter element end caps, forms an enclosure for the facing end of the filter material 27. The external circumference of the receiving part 45 surrounds a ring of uniformly distributed, plate-like supports 47, the planes of which extend in the radial direction and which form the brackets for an annular receiving crown 49, which is located at an axial distance from the receiving part 45 and at a radial distance from the outer side of the remainder of the filter element 13. A guide part 51 is connected to the bottom side of the receiving part 45 at the internal circumference thereof, which guide part has the form of a hollow cone, which extends axially with its tapered end into the inner side 15 and ends at the bottom edge in a rib 53 projecting radially inwards.

The supports 47 continue below the receiving part 45 along the inner side of the guide part 51 as an additional ring of the supports 47, which project radially inwards and extend from the bottom side of the receiving part 45 to the rib 53 on the guide part 51. One of the supports forms a receiving support identified with the reference numeral 55, in which a channel section 57 extends in the vertical direction and which opens at its bottom free end into the inner side 15 which forms the non-filtrate side. This channel section 57 forms a part of a channel run, by means of which the instantaneous pressure of the inner side 15 arrives at a differential pressure measurement device 59 belonging to the filter device. For this purpose, a channel section 61 extending perpendicular to the channel section 57 is connected to the top closed end of said channel section 57, with said channel section 61 extending in the radial direction and opening with its free end 63 into a collection chamber 65, which forms an additional part of the channel run.

The base of the collection chamber 65 is formed by a wall part 67 of a connection region 69 which projects radially from the filter head 3. At the top side opposite the wall part 67, the collection chamber 65 is delimited by a housing cover part 71, which has a radial protrusion 73, which overlaps a radially projecting wall part 75 which forms the side wall of the collection chamber 65. The cover part 71 is detachably connected by means of fastening screws 77 to the filter head 3. As is most clearly shown by FIG. 3, the circumferential edge of the receiving crown 49 is overlapped by a molded seal 79, which has a U-shaped cross section and which forms with its top profile limb 81 the seal with the cover part 71, while the bottom profile limb 82 and the profile support 83 extending axially between the limbs 81, 82 form the seal relative to the filter bowl 7. The molded seal 79 thus forms both the seal of the overall fluid system situated above the tank wall and, because the molded seal 79 extends over the radially projecting protrusion 73, the seal of the collection chamber 65.

For the purpose of continuation of the channel run, a passage 85 is formed in the base of the collection chamber 65, which passage extends through the wall part 67 into the bore 87 of the connection region 69, into which the measurement housing 88 of the measurement device 59 can be screwed. A transverse channel 89 is formed in the measurement housing 88, which transverse channel is connected to the passage 85 and which continues the channel run up to the back end face 90 of a measurement piston 91. It is pretensioned in the measurement housing 88 by means of a compression spring 92 for a movement in the radially outwards occurring backwards direction. The measurement housing 88 is closed by means of an end piece 93 at the radially inner end, which abuts the outer side 17 of the filter element 13 that forms the filtrate side, in which end piece an additional passage 94 is located, by means of which the facing end face of the measurement piston 91 is pressurized with the instantaneous pressure of the filtrate side. During filtering operation the measurement piston 91, which is pressurized on the front end face 90 with the instantaneous pressure of the non-filtrate side by means of the transverse channel 89, thus occupies a piston position corresponding to the differential pressure.

In order to obtain an indication of the piston position, a permanent magnet 95 is arranged on the radially outerlying end region of the measurement piston 91. In the filtering-capable state of the filter element 13, the measurement piston 91 assumes a position under the influence of the compression spring 92, in which position the permanent magnet 95 holds an evaluation piston 96 in an attracted position wherein it contacts thereon. The evaluation piston 96 is displaceable in the measurement housing 88 and is pretensioned by means of a spring 97 for a movement directed away from the permanent magnet 95. The pressure in front of the filter, for example in the form of the pump pressure, always remains the same during operation. Due to the contamination of the filter mat, the pressure after the filter mat is lower in the case of a contaminated filter element than in the case of an uncontaminated filter element. That means that the pressure on the back end face 90 at the measurement piston 91 remains the same, however the pressure on the opposite, front end face of the measurement piston 91 drops, so that the measurement piston 91 moves to the right when viewed in the viewing direction of FIG. 1 and releases the evaluation piston 96. The evaluation piston 46 thus drops away from the permanent magnet 95 of the measurement piston 91, so that the evaluation piston 96 moves outwards in the radial direction and thus supplies an indication of a blocked state of the filter element 13. For a visible indication of the position of the evaluation piston 96, the measurement housing 88 has at the radial outer end a hood 98 consisting of a transparent material, for example made of plexiglass, with marking being able to be provided, for example in the form of color marking, which supply an obvious visual indication of the state of the filter element 13. Alternatively or additionally, an electric signaling can be provided, for example by means of a Hall effect sensor, which recognizes the position of the evaluation piston 96.

The rib 53 at the end of the guide part 51 forming a hollow cone forms a sealing edge 54 for a valve cone 56, which is located on a closure part 58 of a bypass valve. The closure part 58 has the form of a hollow cylinder, which is closed at the end forming the valve cone 56 and there forms the seat for a compression spring 60, which is supported at the other side on the cover part 71. The hollow cylindrical closure part 58 is guided in a circular cylindrical guide wall 62, which extends axially away from the cover part 71 into the guide part 51. In the blocked state of the filter element 13 and with lifting of the valve cone 56 from the sealing edge 54 brought about by the non-filtrate pressure, a fluid path is formed which bypasses the filter element 13, which fluid path leads via the top side of the receiving part 45 to the outer side 17 which forms the filtrate side, see the flow arrow 99 in FIG. 1.

The differential pressure measurement device 59 according to the invention not only allows the detection of a blocked filter element 13; it is in fact also possible to establish that there is no filter element 13 at all in the filter element housing, and it is furthermore possible to achieve, by means of the evaluation electronics to the differential pressure measurement device 59 in the case of a corresponding “tactile design”, the detection of any plagiarized product, which may present a different blockage behavior with different differential pressures compared with the original element from the manufacturer, provided that the particulate contamination to be filtered out of the fluid is similar in both cases. 

1. A filter device comprising a filter housing (1) having a filter head (3) and a filter bowl (7), which housing accommodates a filter element (13) that separates a non-filtrate side (15) from a filtrate side (17), and comprising a differential pressure measurement device (59), which indicates at least a blockage of the filter element (13) during the filtering operation and which has a measurement piston (91) that is guided in a measurement housing (88) in a longitudinally displaceable manner, with the instantaneous pressure of the non-filtrate side (15) being applied to an end face of said piston and the instantaneous pressure of the filtrate side (17) being applied to the opposite end face of said piston, each instantaneous pressure arriving in the measurement housing (88) via at least one channel run (57, 61, 65, 89), characterized in that at least a part (57, 61) of the channel run is arranged in an element cap (43) of the filter element (13).
 2. The filter device according to claim 1, characterized in that that part (57, 61) of the channel run which is arranged in the element cap (43) ends with its one free end at the non-filtrate side (15) of the filter element (13) and with its other free end (63) in a collection chamber (65), which projects from the external circumference of the element cap (43) and which is delimited on opposite end faces in a sealing manner on the one hand by a cover part (71) arranged in a detachable manner on the top side of the filter head (3) and on the other had by parts (67) of the filter head (3).
 3. The filter device according to claim 1, characterized in that the collection chamber (65) as part of the channel run has at the base side a passage (85) formed in the filter head (3), to which a transverse channel (89) extending in the measurement housing (88) is connected, which leads with its other free end to the back end face (90) of the measurement piston (91).
 4. The filter device according to claim 1, characterized in that the measurement piston (91) is pressurized with an energy store, such as a compression spring (92), which seeks to displace the measurement piston (91) in the backwards direction, and in that the front end face of the measurement piston (91) abuts an end piece (93) of the measurement housing (88), which has a passage (94) as an additional part of the channel run, at which the instantaneous pressure on the filtrate side (17) is applied.
 5. The filter device according to claim 1, characterized in that the part (61) of the channel run in the element cap (43) of the filter element (13) that opens into the collection chamber (65) overlaps the top end of the filter element (27) and follows the cover part (71) in a parallel manner and in that the other part (57) of the channel run, arranged perpendicular thereto, is accommodated by a receiving support (55) extending in the radial direction and is guided on the inner side (15) of the filter element (13) which forms the non-filtrate side.
 6. The filter device according to claim 1, characterized in that the collection chamber (65) is a component of an annular sealing system (79), which is arranged at the external circumference on a receiving crown (49), which is held by means of a ring of radially extending supports (47), which are connected to an end-face receiving part (45) for the top end of the filter material (27), and in that a receiving part (45) is delimited at the internal circumference at least partially by a conically extending guide part (51), which extends away from the internal circumference of the receiving part (45) into the inner side (15) of the filter element (13), and in that the supports (47) continue on the inner side of the guide part (51), one of which supports forms the receiving support (55) for the end part (57) of the channel run extending to the non-filtrate side (15).
 7. The filter device according to claim 1, characterized in that the receiving crown (49), the supports (47, 55), the receiving part (45) and the guide part (51), integrally connected to each other, form the element cap (43).
 8. The filter device according to claim 1, characterized in that the sealing system has a molded seal (79) at the external circumference, which surrounds a surrounding wall of the receiving crown (49) of the element cap (43).
 9. The filter device according to claim 1, characterized in that the filter head (3) has, at the point of the intervention of the differential pressure measurement device (59), a projecting connection region (69), into which the measurement housing (88) is screwed at the end face.
 10. The filter device according to claim 1, characterized in that as part of the differential pressure measurement device (59), projecting further towards the outside, an evaluation unit (96, 98) is connected to the measurement housing (88) which is to this extent formed closed, which evaluation unit indicates to an observer, in particular in an optical manner, whether the filter element (13) in filtering operation is blocked or is still capable of filtering.
 11. The filter device according to claim 1, characterized in that the measurement piston (91) of the measurement device (59) has a permanent magnet (95) which, in the filtering-capable state of the filter element (13) and acting against the action of an energy store, in particular in the form of a compression spring (92), holds a permanent magnet of an evaluation piston (96), which is guided in a housing of the evaluation unit (96, 98) in a longitudinally displaceable manner, in a position which it leaves and moves in the direction of an additional position as soon as the permanent magnet (95) of the measurement piston (91) moves away from the permanent magnet of the evaluation piston (96) due to the falling instantaneous pressure on the front end face of the measurement piston (91) brought about by a blockage of the filter element (13). 